The present invention relates to power line carrier communication apparatuses and communication systems, and more particularly to a power line carrier communication apparatus and a communication system in which symbols are transmitted via a power line.
Japanese Unexamined Patent Application Publication No. 2008-172849 discloses a power line carrier communication system. The communication environments of power lines are various depending on places and times, and some communication environments may be very poor in terms of their noise conditions or impedance conditions. Under such environments, the communication standards using the existing OFDM (Orthogonal Frequency Division Multiplexing) (such as G3-PLC and PRIME) are inadequate to carry out favorable communication. Therefore, a robuster communication method is necessary for such environments.
One of the robust communication methods is disclosed in Japanese Unexamined Patent Application Publication No. 2008-172849. According to Japanese Unexamined Patent Application Publication No. 2008-172849, the robustness of the communication method is retained by redundancy on a time axis. For example, when 80 symbols are to be transmitted, they are transmitted by being interleaved by 16 types of carrier frequencies (Refer to FIG. 2 and FIG. 3 in the above patent application publication). Specifically, plural symbol sequences are created by reordering transmission symbols on a time axis. Subsequently, plural input symbol sequences are modulated by different carrier frequencies respectively (Refer to the paragraph 0019 of the above patent application publication). Therefore, time-domain repeated signals are created at a prestage of frequency interleaving.